tomtomdu80, mr.gas and GodmanGen have released a POC of the installation of beta PKG’s on a retail PS Vita, here is a quote from the source:
Here is just a POC of beta pkg installation (these native pkg encrypted with PSP AES keys), we can actually install them on 3.15 !
Here is the proof (uncharted_portable.pkg is a beta pkg which can be found in the leaked SDK)
They are also looking for some PS3 devs to help them with PKG files.
You can discuss it on the forum at the link below:
Proof Of Concept Installation Of Beta PKG’s On PS Vita